When pathological examinations are performed on tissue or the like of humans or animals suffering from disease, generally, after the tissue is sliced into sections with a thickness of 2 to 5 μm and is subjected to various dyeing methods, a microscopic observation is performed to examine the tissue.
At this time, a diagnosis is performed based on information acquired in the past. Particularly, pathology is composed based on a large amount of information with respect to a disease and a form change of the tissue. Accordingly, in order to effectively use the information acquired in the past, it is necessary to cut a sample, which is a test object, along a specific cross-section, and to slice the sample so that tissue required for the diagnosis appears on the surface of the sample.
In general, in order to slice soft tissue and cells so as not to break forms of the tissue and the cells, the sample is embedded in paraffin in advance, and an embedding block is fabricated. Moreover, the embedding block is thinly sliced (is thinly sectioned) to a thickness of 2 to 5 m, and thus, a thin section is fabricated. Accordingly, even when the test object is soft tissues or the like, the soft tissue can be very thinly sliced without destroying the form of the tissue. The thin section is fixed onto a substrate such as a glass slide, and the thin-section sample is fabricated. Generally, an operator performs the microscopic observation on the thin section sample, and performs the above-described pathological examination.
When the thin section is fabricated, two processes such as a preliminary cutting process (rough cutting process) and a main cutting process are performed, and thus, the thin section is cut out from the embedding block. In the preliminary cutting, the embedding block is gradually sliced so that the surface is flattened, and the surface of the sample embedded in the paraffin is exposed. Moreover, in the main cutting, the thin section is cut out to have a predetermined thickness with respect to the surface of the embedding block in which the sample is securely exposed.
Particularly, from the viewpoint of the above-described pathology, it is preferable that in the fabricated thin section, the sample be maintained in a desired exposure state which is suitable for the observation. Therefore, the preliminary cutting is important, and thus, it is necessary to carefully perform the preliminary cutting.
However, since the paraffin embedded with the sample becomes clouded due to crystallization at the time of solidification, after the embedding block is fabricated, it is impossible to confirm in advance from the external view of the embedding block that what form the sample has when embedded in the paraffin. Therefore, when the preliminary cutting is performed, it is necessary that the operator appropriately adjusts a cutting amount of a cutting blade, an angle of a support frame on which the embedding block is placed, or the like while always observing the surface of the sample exposed from the paraffin, and performs adjustment so that a biological sample has a desired exposure state. Restarting of the operation is not possible, and the cutting should be performed dozens of times or more until a desired surface is exposed.
Therefore, skill and attentiveness for a long period of time are required, and there is a large burden on the operator.
A thin section fabrication apparatus is suggested which effectively performs preliminary cutting on an embedding block so that a biological sample in the embedding block is securely maintained at a desired exposure state (for example, refer to Patent Document 1).
In the thin section fabrication apparatus disclosed in Patent Document 1, an epi-illumination system that radiates epi-illumination light to the embedding block, a diffusion illumination system that radiates diffusion illumination light to the embedding block, and an imaging unit that images the embedding block under the epi-illumination light and the diffusion illumination light are provided, a state in which imaging data of the embedding block imaged under the epi-illumination light and imaging data of the embedding block imaged under the diffusion illumination light overlap each other is displayed on a monitor, and thus, an operator can easily set a cutting amount, an inclination angle, or the like of the embedding block at the time of the preliminary cutting while confirming with the display of the monitor.
When the epi-illumination light is radiated to the embedding block, a luminance difference is generated between a portion of an embedding agent such as the paraffin and the exposed portion of the biological sample. On the other hand, when the diffusion illumination light is radiated to the embedding block, the light enters the inner portion of the embedding block, abuts the biological sample which is not exposed to a cutting surface, and is reflected.
In the thin section fabrication apparatus disclosed in Patent Document 1, by focusing attention on the above-described characteristics, the imaging data obtained under the epi-illumination light and the imaging data obtained under the diffusion illumination light are overlapped with each other and displayed on the monitor. Accordingly, the operator can accurately understand the state of the surface of the embedding block and the state of the biological sample in the embedding block.